Posted
by
timothyon Friday May 28, 2010 @02:01AM
from the was-in-the-neighborhood dept.

schliz writes "A radio telescope in New Zealand has joined five in Australia to challenge Southern Africa to host the international Square Kilometer Array (SKA) in 2012. The newly connected telescope in Warkworth, New Zealand (PDF), is connected to an Australian data processing facility via a 1 Gbps network. Each telescope reportedly produces up to 1 Tb of data per hour of observation. IBM expects the whole of the SKA to produce an exabyte of data per day."

The newly connected telescope in Warkworth, New Zealand (PDF), is connected to an Australian data processing facility via a 0.000048828125 LOC/s network. Each telescope reportedly produces up to 0.05 LOC of data per hour of observation. IBM expects the whole of the SKA to produce 52428.8 LOC of data per day.

I do not understand what is so interesting about this. Another dish added to various international VLBI networks. There is also one such dish near Urumqi in China in a very remote area. There are so many of these kind of dishes around the world. Even here in the Netherlands we have one. But we also have LOFAR [lofar.org], which is also capable of producing large amounts of data everyday. This kind of systems usually only operate for short periodes and the data produced are immediately processed and only the results are stored.

For your information, the LOFAR system also processes data immediately. All the stations are connected with 10Gbit networks to the central processing system in Groningen.

Each LOFAR antenna produces 0.8 Gbyte of data per second. When finallized, the system will consist of about 7000 antenna spread out over about 40 field most of which are in the Netherlands, but about ten of them will be abroad. I understand that each field will perform some preprocessing before the data is send to the central processing unit where it is correlated and further reduced before it being stored and made available for off-line processing. See here [lofar.org] for a detailed description.

Well, that's partially true. The online/realtime processing doesn't store the data. We have the data coming in at about 150 Gbit/s into the BlueGene supercomputer (34 TFlop), which does initial realtime processing and writes resulting files at about 50 Gbit/s on a roughly 1 Petabyte intermediate storage system for offline processing. From there it gets initial processing/calibration and a factor of 16 to 64 reduction in size on the offline processing cluster (about 200 8core machines). Also some inspection of the data is done for quality assessment, and sky images are made. If the quality is good, the resulting data and images are moved to out 4+ Petabyte long term archive, where further processing can also be done to achieve publication ready results.On average we are expected to be producing about 20 TB/hour raw data, and about 700 GB/hour data that gets archived (life time of more than a week).

As I speak we are 2 weeks away from the system being opened by the Dutch Queen, and we are operating on about half the above numbers with about 25 antenna fields online. By the end of 2010 we should be operating at full strength. Also, those numbers are from the top of my head, so I might be off a bit here and there.

I work on millimeter- and submillmeter-wave frequency radio telescopes in Arizona that occasionally do VLBI runs at 1.3mm (230 GHz). We don't have anything like a 1Gbps data link; it's more like 10 Mbps. It's hard to get the phone company to install a fiber cable run up a mountain.

Our VLBI data are stored on hard disks at a rate of ~1 Gbps,
then correlated later on some big computer back east. We have to wait days to learn if interference fringes were detected!

On a distantly related note I once worked with a guy who was doing synthetic aperture radar from a sled on the antarctic ice cap. On his return he planned to spend weeks manually reducing the data so I wrote a fortran program for him which did the whole job in three hours on VAX 11/730.

It's all politics. There's the environmental impact problem. The folks who arranged for our underground power line really screwed up by not putting a fiber in the same trench; now it's virtually impossible to get the Forest Service to permit additional work. Four words: Mount Graham Red Squirrels!

now it's virtually impossible to get the Forest Service to permit additional work.

- Buy the fiber roll.
- Throw some green and brown paing buckets over it.
- Before it dries, throw in little branches, leaves, and red squirrels.
- Buy a ninja costume, a shovel and a pair of night vision goggles.
- Every night, go to the forest, lay out some meters of underground fiber and hide the camo roll.

If someone finds you, dressed as a splinter cell ninja, carrying a shovel and an oversized rotten donut, you can make a deal: if he finds out what's your PhD on, you give him $5k, if he doesn't, he leaves you alone.

What's more important? You can have internet or the endangered Mount Graham Red Squirrels can have an environment free of redneck construction workers fucking everything up? You think maybe those laws exist for a reason?

One of the stories I heard, about another VLBI telescope, was that getting to within about 15km was easy, but the last stretch costed about 400,000 euro. These telescopes tend to be in rather inaccessible terrain.

I live in Warkworth, at one point there actually were sheep grazing very near it but they got moved a while back. I did on one occasion go for a night time bush exploration on the hills surrounding the telescope. The dishes look very cool at night.

In arrays, you want _many baselines_ (telescope to telescope distances) and you want them to be _long_, because that will make your image better. It shouldn't be as large as the earth-radius though, otherwise you can only observe a few hours per day.

The SKA is being built in South Africa or Australia, and New Zealand would like to provide an "addon" to the SKA -- if it is going to be built in Australia --, that will provide a *huge* improve on the baselines involved. Tests have shown that the imaging capabi

It shouldn't be as large as the earth-radius though, otherwise you can only observe a few hours per day.

I'd think you'd want a baseline nearly as long as an Earth diameter, as long as you can switch elements in and out of the array as they come into view of the target. With a ring all the way around the planet and the ability to continuously reconfigure the array in real time you could keep equatorial objects under continuous observation. Resolution would vary throughout the day, though, as it is not (yet

While you are correct, long baselines come with a couple big drawbacks:- You need higher time resolution to prevent bandwidth smearing.- You need intermediate length baselines as well, or your uv coverage will be poor.- To grid your data in the uv plane becomes very hard as the grid becomes very large.

This means that the size of the data you need to manipulate and processing requirements go up very quickly with longer baselines. For LOFAR we now have baselines of about 1000km and we will go even longer to 2

Disclaimer: I work for ASTRON operating the 14 25m dish 3km WSRT, 7000 antenna 44 station 3000km LOFAR and the 3 station EMBRACE SKA demonstrator project. Although I'm not an astronomer.;-)I just visited a friend of mine at the University of Canterbury in ChristChurch, working with the MOA, astrophysics is a small world in NZ, good luck getting involved in SKA!

I will contact you guys soon with some software system questions re EMBRACE... if you could leave your email address in a comment on my blog that'd be great. I'm researching scheduling systems (and probably simulators as well) for the SKA. Cheers

"With the central core of the SKA located in this south-western part of the country the remote antenna stations would be located on easterly and northerly log spirals up to 3000 km away (Namibia, Botswana, Mozambique, Madagascar Mauritius, Kenya and Ghana)." skatelescope.org [skatelescope.org]

I've been following the bid process for SKA for quite a few years. As far as I can tell South Africa (together with its other Southern African partners) have a clear advantage over Australia (now together with NZ)

There are a few reasons for this:

1. The passing of the South Africa's Astronomy Geographic Advantage Act [ska.ac.za] in 2007 declares almost the whole of the Northern Cape province (an area about 1.5 times that of the UK) into an astronomy advantage area. Amongst other things it means that light pollution will

1. The passing of the South Africa's Astronomy Geographic Advantage Act [ska.ac.za] in 2007 declares almost the whole of the Northern Cape province (an area about 1.5 times that of the UK) into an astronomy advantage area. Amongst other things it means that light pollution will be limited and that the whole area will eventually be turned into a radio quiet zone.

The Australian desert is an empty, extremely radio quiet right now, and has also been declared as a no-building zone. In comparison, the million cell towers make South Africa is extremely noisy.

2. Much of the technology used in South Africa's pilot program (MeerKAT [ska.ac.za]) will be directly useable in SKA. By comparison, the Australian Square Kilometre Array Pathfinder project has much less tech that will be useable in SKA without major redesign and modification.

I'd be interested in hearing more about that. Why is the one more directly reuseable?

3. Price. From the start keeping the price down was a very high priority goal for the SA bid. E.g. they developed a new process to manufacture the dishes that is much cheaper than conventional methods. Now, after the credit crunch where many scientific budgets are getting cut, this strategy is paying off.

Disclaimer 1: I am a South African and therefore far from neutralDisclaimer 2: The last time I read extensively on this is more than six months ago, so if there were significant developments recently then I might not be aware of them

Interesting.

4. Baselines: The NZ-AUS baseline is going to be extremely long.

There is also a "5. Politics & political stability", which is a bit more complex and probably has some FUD.

The last word definitely hasn't been said about this yet, but I tend to agree that Australia slightly edges out SA at the moment. As for the technology, there are a few more options than only MeerKAT or ASKAP technology. Here at ASTRON we work on EMBRACE and LOFAR.